The production of alternative fuels, generically called bio-fuels, is currently dominated by the conversion of high cost feed substrates such as sugar cane, corn, rapeseed, palm oil and other terrestrial crops predominantly used as food for human/animal consumption. While the technology exists to convert these feed-stocks to bio-fuels, there is not sufficient arable land or fresh water resources to meet our society's enormous demand for energy.
The United States alone uses over 168 billion gallons of gasoline per year. The current U.S. output of bio-fuels, particularly ethanol made from corn, covers only 5 billion gallons per year and is representing just 3% of the gasoline used in the U.S. In addition, the ethanol from corn production has triggered a 50% increase in the market price of corn on global commodity markets.
The second most predominant alternate renewable energy source has been the conversion of cellulose based waste products to bio-fuels. The relative limited availability of biomass supply, its high cost of transportation to the processing facility, as well as the initial investments, has limited the scale of this technology to less than 0.06% of the U.S. needs.
The third and the most promising alternate renewable energy source is the use of photoautotrophic organisms, such as microalgae with high content of oil, to produce bio-fuels. The primary benefit of this technology is the combining of the process of the conversion of solar energy into cellular biochemical energy. Photoautotrophic organisms are those that can survive, grow and reproduce with energy derived entirely from the sun through the process of photosynthesis. Photosynthesis is essentially a carbon recycling process through which inorganic carbon dioxide is combined with solar energy, other nutrients and cellular biochemical processes to synthesize carbohydrates required to sustain growth. Photosynthesis occurs in plants, algae, and many species of bacteria.
Previous efforts for larger scale production have focused on growing photoautotrophic organisms in land-based open ponds or raceways that provide similar growing conditions found in nature. A major drawback of this approach is that growing conditions cannot be well controlled, resulting in uncertain production outputs, batch contaminations and other significant technical challenges to bring the micro-algae growing and harvesting technology to a commercial reality.
Below are the six most important reasons why the current land-based microalgae growth and harvesting system have failed to become a significant renewable energy source:
1. Water requirements. Microalgae need a lot of water—they grow in it. Water evaporation is a major detrimental factor.
2. Light requirements. Microalgae need a lot of light, and to receive it, they typically require a flat waterbed no deeper than four inches but with horizontal surface area of hundreds of square yards. That means a lot of perfectly flat land must be converted into waterbeds and filled with water in order to accommodate microalgae growth. The logistics addressing the construction of thousands of acres of flat waterbeds and the related water requirements are overwhelming and cost prohibitive. One of the main concerns related to the land allocation for building wide-scale flat waterbeds is the potential displacement of croplands currently used for food supply.
3. Water temperature factor. Microalgae growing season is largely dependent on location and, aside from tropical areas, is limited to the warmer months. Large day and night temperature variation specific for desert climate are extremely detrimental in microalgae growth.
4. Carbon dioxide requirements. Microalgae cannot use directly the atmospheric carbon dioxide. The carbon dioxide, crucial for algae production yield, must be dissolved in water. For stationary flat waterbeds the logistics and energy requirements to constantly provide microalgae culture with the needed carbon dioxide are cost prohibitive.
5. Contamination factor. Microalgae are very vulnerable for being contaminated by other microalgae species and bacteria. Most often the species of microalgae that have the highest oil content are not necessary the strongest and quickest to reproduce.
6. Energy factor. The current cost for over-land or on-shore lines for microalgae mass production, including fertilization, harvesting, transportation, and storage are extremely high and non-competitive with the existing fossil fuel economy.
One point of novelty of the present invention is that it economically addresses all the above-mentioned problems associated with land-based microalgae production systems while also being posed to facilitate a significant cost reduction in producing renewable energy source capable of competing with existing fossil fuel industry.
A search of the prior art did not reveal any patents that read on the instant invention. However, the following U.S. patent applications are considered related:
U.S. patentapplication No.Applicant(s)Filed Date8,161,679Albus et al.Dec. 21, 200912/316,557Trent et al.Dec. 5, 20087,980,024Berzin et al.Apr. 25, 2008
Albus et al. teaches an open ocean floating algae farm built around a ship. The ship provides propulsion power for navigation, storage capacity for material and algae products, machinery for harvesting and processing the algae, housing for crew, and facilitate the maintenance of the floating farm. The invention also comprises transparent tubes that circulate a broth of seawater saturated with CO2, nutrients and algae. The circulation path flows from the ship through the tubes and back to the ship where the algae are filtered out ready to be processed. The transparent tubes circulating the algae broth are supported by a matrix of tubes filled with seawater that is neutrally buoyant and submerged just below the ocean surface.
Trent et al. teaches a method for producing hydrocarbons, including oil by processing algae and/or other microorganisms in an aquatic environment. This method employs flexible bags containing nutrient and seeds of algae growth. The bags having CO2/O2 exchange membranes are suspended at a controllable depth in an aquatic field. The algae are cultivated and harvested in the bags.
Berzin et al. teaches photo-bioreactor units flowing on a body of water such as a pond or a lake containing a liquid medium comprising at least one species of phototrophic organisms. The photo-bioreactor units are formed of flexible, deformable material and are configured to provide a substantially constant thickness of liquid medium. In certain embodiments a barrier between the photo-bioreactor units and the body of water upon which the unit is floating controls the heat transfer between the liquid medium and the body of water.